Conventionally, in order to output a melody or a beep sound when an audio output device such as a television and an audio device is powered on/off or mode-switched, desired sound data previously stored in a ROM of the audio output device are read from the ROM. This sound data is subjected to a signal processing and then output through a speaker whenever a power on/off or a mode switch button is pressed. As a related technique to the above-described method, an automatic level control (ALC) for automatically controlling a volume of an audio signal is conventionally known.
However, in the above-described method in which the desired sound data are previously stored in the ROM of the audio output device, a large memory capacity of ROM is required to output various sound. Further, once the sound data are written to the ROM, it is significantly difficult to add new sound data to the ROM or change the sound data stored in the ROM.